Field of Invention
The present invention relates generally to a vertical takeoff and landing (VTOL) winged vehicle and, more particularly, to a ducted, single-axis, oblique-rotor, flying vehicle that is controlled predominately by vanes in vertical flight mode and a combination of vanes and aerodynamic surfaces when in horizontal, or a wing-lifting, flight mode.
Prior Art
Flying machines that can takeoff vertically and hover have been around for over a century. To date, the most practical configuration of these machines is the helicopter. Although there have been variations of the helicopter design, all have similar mechanisms. The reasons for the success of the helicopter is the light-weight structural configuration of the rotor system that allows for a low disc loading and the ability to auto-rotate in the event of engine failure.
The helicopter has several limitations, however, including speed and range, because of the rotor's direct exposure to the freestream airflow. Another limitation of the helicopter is the inherent danger of exposed main and tail rotor blades to ground personnel. Finally, noise and airframe vibration is synonymous with the helicopter.
Humans have trying to solve these problems and create a more esthetically pleasing form of the helicopter ever since its creation. An early design conceptualized a propeller housed in a shroud and used a minimum number of vanes for control. See U.S. Pat. No. 1,822,386 (Andersen). Other early designs tried to encapsulate a large rotor with vanes, above and below, to direct flow and provide control. See U.S. Pat. No. 2,777,649 (Williams). Later, single and multi-rotor platforms were studied. See U.S. Pat. No. 2,955,780 (Hulbert). Winged, tandem-rotor platforms were also proposed. See U.S. Pat. No. 2,968,453 (Bright). Piasecki Aircraft Corporation built several prototypes of the wingless, tandem-rotor platforms. They were controlled by using both vanes and differentially adjusting the collective pitch control between each rotor. See U.S. Pat. No. 3,184,183 (Piasecki). More recent designs of the VTOL aircraft have been around for decades without becoming practical. An example of this is the Moller Skycar. The design requires very high power to weight ratios and complex mechanical control systems. See U.S. Pat. No. 5,115,996 (Moller).
Work has continued on the tandem rotor platform vehicle in recent times. These configurations are proposed with wings and without, with gamboling rotors and a multitude of vane configurations. See U.S. Pat. No. 6,464,166 (Yoeli), U.S. Pat. No. 6,883,748 (Yoeli), U.S. Pat. No. 6,892,979 (Milde), U.S. Pat. No. 7,246,769 (Yoeli), U.S. Pat. No. 7,249,732 (Sanders), 2009/0084907 (Yoeli), 2010/0270419 (Yoeli), U.S. Pat. No. 7,857,253 (Yoeli), 2011/0049306 (Yoeli), 2011/0168834 (Yoeli), U.S. Pat. No. 8,651,432 (De Roche). These concepts may have merit for short range and endurance, however, the design is inherently inefficient for both lifting capacity and horizontal flight.
Another concept that has recently been proposed, because of advances in electric power storage and reduction in motor weight, is the use of multiple, small, electricly-powered rotors, either shrouded or un-shrouded, to provide lift and control. See US. Pat. Appl. No. 2011/0042509 (Bevirt). Their design proposes that multiple rotors be used to provide differential thrust to control the vehicle. There are at least two drawbacks to these designs. Firstly, the inherent propulsion efficiency of multiple, small fans, shrouds, and electric motors will be limited. Secondly, the whole vehicle must be rolled or pitched away from level in order to translate or compensate for wind near the ground. This coupling of orientation and translation has drawbacks if the vehicle is to be used for the transportation of packages to and from the ground.
Objects and Advantages
Point-to-point transportation of products and people have been dreamt about for centuries. The idea of stepping into a personal flying machine that can take someone directly to where they want to go, all while watching the world from above, is alluring. Recently, corporations have even set goals to autonomously deliver packages to individual residence from the air. The present state of the art in air vehicles has prohibited either of these visions from realization. There is currently inadequate infrastructure to safely direct the number of flying machines required for mass movements of everyday people and goods. There is also a lack of viable aircraft that can safely be flown from or into residential or commercial locations, much less, ones that can be done at a price people can afford. A flying machine that will someday make point-to-point transportation a reality will be controlled autonomously. These machines must be able to land in a multitude of locations across a densely populated area since current airports do not have the areal capacity to park all the vehicles of those visiting and inhabiting a city. Flight paths of vehicles will be in close proximity and precise navigation and control will be required to safely integrate into the congested airspace in both visual and instrument meteorological conditions.
Flying machines that takeoff and land vertically have evolved into two districted groups, those with relatively small, enclosed rotors or lift nozzles, such as the Joint Strike Fighter or Harrier, and those with large rotors, such as helicopters. The first group has very high disk loading or nozzle pressures and requires large power-to-weight ratios to achieve vertical flight. They need state-of-the-art, expensive, fuel inefficient engines that produce noise levels much beyond what are acceptable in residential or business communities. The second group of vehicles, the helicopter, can fly vertically on much lower-power and use relatively efficient engines; however, they require trained personnel to be in their vicinity because of the dangers from exposed rotors. Helicopters also have inherent limited range and speed capability. Hybrid vehicles, such as the Osprey or Eagle Eye, using tilt-rotor configurations, have been introduced and used in service but this configuration requires very expensive turbine engines and complex mechanical systems for them to fly safely. And, they still suffer from the dangers of exposed rotors.
Electric, multi-rotor, flying vehicles have recently been introduced to the public for entertainment or used as a photography platform. These machines have only become available because of the miniaturization of electronic components and improved battery technology. They can be made with propulsion redundancy if enough rotors are employed; however, this adds complexity and weight. This configuration still suffers from exposed rotors which can be dangerous if scaled to a size that is useful to carry cargo or people.
Accordingly, there are several objects and advantages of my invention. The vehicle's novel oblique rotor configuration with forward facing inlet is the simplest mechanical system that can provide efficient vertical lift and horizontal propulsion. Multiple rotors rarely provide additional redundancy since failure of any mechanical component in a rotor system general means loss of the vehicle. The bifurcating duct that integrates the invention's payload location and also separates the left and right vertical control vanes, provides an optimum configuration for tomorrow's transportation needs. This simple mechanical rotor system using a plurality of vanes in a redundant configuration produces a reliable vehicle using inexpensive servos for control. This configuration also allows the vehicle to decouple attitude and translational flight control so that it can translate in a level position or stay stationary in a slight unlevel attitude. This feature is needed for package pickup and delivery and provides advantages for weapons delivery. Another advantage of this configuration is that it has a medium disc loading which can be powered by a hybrid electric-internal combustion powerplant and will produce little noise compared to current turbine-powered machines. Also, the rotor is completely enclosed, disallowing inadvertent contact with people or property. This configuration, integrated with wings, allows this vehicle to have much greater range and endurance than either a helicopter or any other enclosed-rotor VTOL configuration. The novel rotor pitch control mechanism in this invention allows for this simple rotor configuration while maintaining triple redundant collective control. Also, the geometric configuration of the vane installation decouples the vane control servo from the vane while the vane is in the stowed position and still being loaded by aerodynamic forces.